WattMaster WM-WCC3-TGD-01B - Manual (Page 797)

Operator Interface
VAV/Zone Controller Technical Guide
29
Other Checks
Space Temperature Sensor
If the Space Temperature Sensor is not reading a valid temperature, fi rst
make sure that the connector is fi rmly plugged into the female connector
on the board and that the Space Temperature Sensor is wired correctly.
If the problem persists, try swapping the sensor with a known good
Space Temperature Sensor. If that sensor works when connected to the
VAV/Zone Controller board, you can assume you have a defective or
damaged sensor.
Supply Air Temperature Sensor
If you suspect the Supply Air Temperature Sensor is not reading cor-
rectly, make sure the wiring terminal connections are tight and that any
wiring splices are properly connected. You can check the operation of the
Supply Air Temperature Sensor by measuring the resistance or voltage
using a digital multimeter. Set the meter to DC Volts. Place the positive
probe on the AIN terminal and the negative probe on the GND terminal.
Read the DC Volts and fi nd that voltage in Table 6 on page 32. Read the
temperature corresponding with that voltage and determine if this is close
to the actual temperature the sensor is exposed to. If the temperature from
the chart is different by more than a few degrees, you probably have a
defective or damaged sensor. You can also check the sensor resistance
to determine correct operation. To read the resistance, set the meter to
Ohms. Unplug the sensor connector from the board and measure the
resistance across the disconnected wires. This resistance should match
the corresponding temperature from Table 6 on page 32.
Airfl ow Sensor
If the Airfl ow Sensor seems to be reading incorrectly, fi rst check the
Airfl ow Sensor’s modular cable connector and be sure it is fi rmly con-
nected to its mating connector on the VAV/Zone Controller board.
Check the Airfl ow Sensor tubing connections at the airfl ow pickup
tubes. The high pressure port of the sensor needs to be connected to the
upstream pickup tube. The low pressure port of the sensor needs to be
connected to the downstream pickup tube.
The “Box Size Constant for Airfl ow @ 1” WG” setting under the con-
fi guration settings for the VAV/Zone Controller must be set to a number
other than 0. This number is normally referred to as the “K” factor and
is supplied by the terminal unit manufacturer. It represents the airfl ow
through the box inlet at 1” W.G. constant static pressure. This factor
must be entered in the confi guration screen or the airfl ow through the
box will be incorrect. If this is set to zero the VAV/Zone controller will
be in Pressure Dependent mode.
If none of the previous procedures solves the problem, remove power
from the VAV/Zone Controller. Shut down the HVAC unit supplying the
duct that the VAV/Zone damper is located on. Be sure that no airfl ow is
present in the duct. Reapply power to the board and wait for the VAV/
Zone Controller to run through its calibration sequence. Restart the
HVAC unit and check the VAV/Zone Controller CFM readings. If the
CFM reading still seems to be in error, you probably have a defective
Airfl ow Sensor and will need to replace it.
Actuator
Check the Modular cable between the controller and the actuator. Be sure
both ends of the cable are fi rmly connected to the mating connectors on
the actuator and the VAV/Zone Controller board. Be sure the damper
moves freely and is not bound. Do this by pressing the actuator clutch
button and rotating the damper shaft in both directions to verify smooth
operation. If binding is present, fi x the problem as required. Remove
power from the VAV/Zone Controller. Reapply power and observe the
damper rotation. If the actuator does not drive the damper in both direc-
tions, the actuator is probably defective or damaged. Another test that can
be performed is to swap cables with another known operating actuator
to determine if the cable could be bad. If the problem goes away, you
have a defective cable that must be replaced. You can also try swapping a
functioning actuator with the suspected defective actuator. If this solves
the problem, then the defective actuator will need to be replaced.
Expansion Board
If the Expansion Board does not seem to operate correctly, fi rst make
sure the modular cable between the Expansion Board and the VAV/Zone
Controller is fi rmly connected at both ends. Be sure that the Expansion
Board has been confi gured correctly. The Expansion Board must be
confi gured before it will operate. You must confi gure it for the number
of heat stages, and if this is a fan terminal, whether it is a Series or Par-
allel Flow fan terminal. On a single duct non-fan terminal unit, when a
call for heat is initiated, the LED labeled RLY2 should light up. If the
Expansion Board is confi gured as a fan terminal, on a call for the fan,
the LED labeled RLY1 should light up. If the LEDs do not light up, the
Expansion Board is probably defective and must be replaced.
Troubleshooting